Louis IX was King of France for the last few decades of the 13th century. His reign marked the end of the 'direct' Capetians and the beginning of the Capet-Orleans dynasty. Much of his reign was consumed by the Berry War, a long drawn-out but largely low-intensity struggle for dominance over the County of Berry, and a vicious short war with Anglia.

Berry had been French property but after the Treaty of Compiegne it had been given to a branch of the Champagnian ducal family and was quickly downgraded to a fief of Champagne. France of course resented this but had directed much of its energies northward opposing Wessex in Normandy or Anglia in Flanders. On Catherine's succession to the throne in 1258 Champagne essentially renounced its fealty to the French crown and earned an invasion in response.

This early stage of the Berry War was conducted by Catherine's husband, Robert of Orleans, but when Robert died at the siege of Vierzon in 1264 Louis quickly moved to seize the levers of power pushing his sister-in-law, and cousin, to the side. Recently widowed, he would take a Byzantine princess, Theodora Diplosynadene, as his second wife and her supposed 'exotic beauty' helped solidify Louis' power base.

The French nobility, and clergy, were largely happy with this transfer of power. It solved any qualms they may have had about swearing fealty to a woman and forestalled any immediate issues of inheritance. In the wider Francian realm however his seizure of power was taken as a opportunity to repudate any pacts or fealty to France. Auvergne for instance had been quietly supportive of Catherine, as Philip III had bribed Count William X with the title of Duke. Now however William X felt no loyalty to the 'usurper' Louis and allied the powerful Duchy with Champagne, then promptly invaded Berry and largely eradicated any gains Robert and Louis had made over the previous years. Peace was agreed to though both Champagne and Auvergne refused to give any fealty to Louis.

After multiple false-starts and a baron's war to content with Charles III of Anglia finally could refocus his attentions on France in 1281. A furious war followed and after the defeat at Pontoise just outside Paris in April 1283 Louis was forced to cede Artesië to Anglia for good. The mood in the French court following this defeat soured, several nobles actively rebelled and Louis' authority was not fully restored until 1287. Champagne had taken the nobles' revolt as an opportunity to punish France further and occupied several towns in eastern Brie. Louis' checking of their siege of Leon would largely bring the nobility back around to his rule and a full-blown war was soon back in motion. A temporary peace was agreed to in 1294 but war restarted two years later.

This last phase saw Champagnian forces swept from Berry and finally, Reims besieged. In 1300 a final peace was agreed to; Berry would become a French province once more.

With the annexation of both Orleans and Berry in relatively quick succession Louis immeasurably improved France's position. After decades of apparent supremacy Champagne was largely broken as a rival to France and would increasingly rely on the Empire, or its immediate neighbours, for its survival. On the French side the loss of Artesië was largely of no issue seeing as France had barely any authority there anyway. Dying in 1302, his successor, the gloomy Louis X, would attempt to build on this success with mixed results.